The present invention relates to methods and apparatus for cleaning of pressure filter elements, and more particularly to a method for cleaning filter elements which may be utilized for alluvial filters.
Filter residues or so-called filter cakes accumulated on the surfaces of individual plates or candles constituting a filter element must be usually removed from the filter at the end of the filtration cycle.
In the prior art methods for cleaning filter elements, the filter cakes are normally removed from the filter plates by means of vibration applied to the filters. For this purpose, vibrators are mounted in the filter elements, which vibrators are used after the end of the filtration cycle. Due to vibration, filter cakes fall down from the mostly vertically positioned filter plates. The disadvantage of this method resides in that the filter elements are themselves subjected to mechanical vibrations in the area of the central shaft on which the filter plates are usually supported; these vibrations can deteriorate the cloth of the filters.
A method of cleaning alluvial filters is disclosed in the Federal Republic of Germany Pat. No. 1,761,796. In this method, the lateral sides of the filter elements are subjected to application of static pressure and after a predetermined static pressure potential has been built up oscillating pressure is applied to the filtering elements in the direction opposite to the filtration direction. The disadvantage of this method is that the filter cloth is subjected to excessive loads due to oscillating pressures acting on this cloth; these loads can cause deterioration and even cracking of the filters.